Season liberally with salt and pepper. Saute 3 to 5 minutes, until mushrooms are lightly golden.

Preheat broiler to high.

To mushrooms, add flour and stir, cooking 2 minutes. Whisk in stock, then stir in cream.

Bring cream to a bubble, then stir in 2 cups of 4 cheese blend. When cheese has melted into sauce, add tomatoes. When sauce comes to a bubble, remove from heat and adjust seasonings, adding hot sauce if desired.

Combine cheese sauce with sausage and pasta, transfer to baking dish, casserole or oven safe serving platter. Sprinkle remaining 1/2 cup of 4 cheese blend and the grated Parmesan over the top and brown under hot broiler.